Four Boston-area residents — a celebrated novelist, a Harvard economist, a pediatric neurosurgeon, and a man who carves, shapes, and threads some of the world’s most finely crafted instrument bows — are among 23 people worldwide chosen to be the 2012 MacArthur Fellows and recipients of the foundation’s “genius grants.”

The grants, disclosed Monday,
are awarded annually based on nominations by those considered to be at the top of their fields. Recipients, chosen for their intense dedication and unique approaches to their professions, each receive $500,000 from the Chicago foundation.

The local winners are Junot Diaz, an MIT creative writing professor and Pulizer Prize-winning novelist; Raj Chetty, a professor of economics at Harvard; Benjamin Warf, a pediatric neurosurgeon at Boston Children’s Hospital credited with revolutionizing the treatment of intracranial diseases; and Benoit Rolland, who has been making bows for stringed instruments for 41 years.

A grateful Rolland, 58, said he has a bit of trouble accepting the “genius” label. Like the ancient Greek philosophers, he tends to think that people are not geniuses, though they may possess genius in the form of a skill or talent.

“So while I am flattered, the genius is not me,” he said. “It is in the sound the bows generate when they are well-crafted and used properly.”

Diaz, 43, who recently released a new collection of stories called “This Is How You Lose Her,” sees the honor in a similar way.

“I can only tell you that if I see a genius, it is in my material and the inspiration for my writing — the lives and history and story of Hispanic peoples and our journeys on this planet, particularly to the United States,” Diaz said.

Warf, 54, worked for about six years in Uganda, where he developed a new way of treating infants with hydrocephalus that has become the standard of care at Boston Children’s Hospital. He also began to unravel the causes of infections that cause the condition, work that he hopes will lead eventually to a means of prevention. He planned to use his award to spend more time in Africa and on related research projects based in the United States.

“I really feel like this can be a turning point in what I’m able to do,” Warf said.

An economics wunderkind since his early 20s, Chetty, 33, has done studies relating to unemployment, education, and other areas of public policy and said the real value of his work is found in affecting the way people live.

“While I don’t work alone — I work in a team — the great thing about my work, the thing I love most about it, is that it could help governments adjust policies that affect average people where they live — when they’re shopping for groceries, when they’re deciding on a course for medical care, or deciding where and how to live.”

Of this year’s local recipients, however, it is Rolland and his rare craft that may be the most unusual.

His grandmother was a famous concert pianist in France. And by the time he turned 7, she had him playing the instrument. By 9, he was a violin student at the Versailles conservatory. And by 16, he was a graduate of the Conservatoire de Paris. But the more he played, the more fascinated he became with the stick and horsehair that generated the sounds. He soon gave up the notion of a career as a musician and committed himself to making bows.

“It is an ancient craft worldwide, but especially treasured in France,” Rolland said. “And I have no better explanation than that I simply love the bow. It is necessary. So important. Much like the instruments they serve, I see the bows as living entities, not unlike muscles in the body.

“You move them differently, they produce different sounds. You shape them differently and mold them differently and the results vary,” he said.

If his explanation seemed steeped in emotion, it is.

In 1982 Rolland moved for several years to Île-de-Bréhat, a tiny French island best known for being a dark sky community — so free of light pollution that residents can practice naked-eye astronomy — and for its silence.

“There are no automobiles on Bréhat — to this day,” Rolland said. “And I went there, because it is difficult to create in noise and chaos. Beauty comes from quiet. So does music.”

As pleasant as Bréhat may have been, Rolland’s time on the island was also a sacrifice. “I made 12 prototypes of a bow while on the island, and I missed seeing my daughters grow up for a period of their lives. I believe though that they understand that music is a gift to us and that I was trying to make that gift more accessible to more people.”

Christine Arveil, Rolland’s wife, said it isn’t uncommon for him to spend up to 12 hours a day, seven days a week in his home studio in Watertown. There Rolland fashions the Brazilian Pernambuco wood that comprises the handles of violin, viola, and cello bows. He painstakingly threads the taut horse hair ribbon that is drawn across an instrument’s strings and lovingly shapes the metal “frog” that allows musicians to alter the pitch and tone of their playing by sliding it along the strings.

He does not own a television, because it would be a distraction. He relaxes by playing violin, writing music, and sailing. He only occasionally has time to read a book for relaxation and not research.

“I know it seems like a cliche,” Arveil said. “But he loves the bows and dotes on each one as a child . . . ”

For all the care he puts into bow making, Rolland’s affinity for science and preservation may have brought him to the attention of the MacArthur selection committee.

In the early 1990s, concerned that the Pernambuco tree, from which bows have been made for centuries, was facing extinction, Rolland did the unthinkable: created a bow of composite material.

It struck Rolland, an avid sailor, that if seaworthy boats can be constructed of carbon fiber, so could bows. Carbon fiber bows are also less expensive (Rolland once crafted one that cost $15,000), making it possible for good bows to go to promising young musicians.

Still, Rolland said his composite bow research “raised eyebrows” until he completed a few prototypes and was able to show what they could do.

“It always comes back to the instrument and to the bow and the sounds they make when brought together,” he said. “So when I was able to show how my carbon fiber bows also produced great sounds they were embraced by the few who got to play them.”

A dispute with his manufacturer prevented Rolland from mass-producing his composite material bow, but French violinist and jazz composer Jean-Luc Ponty called it the “21st-century bow.”

He also retained ownership of the carbon fiber bow’s most notable feature — an inner tension mechanism that allows musicians to modify the camber or angle of their bows at will, even while they are on stage playing, allowing them to dramatically alter their sounds while playing.

“That invention alone is a point of great pride for me,” Rolland said. “I will treasure it not to celebrate myself, but because I really believe it was the factor that convinced many traditionalist, stringed-instrument players that it is OK to break away from a tradition in the interest of preservation and still make amazing music. I really believe that creation could help win over this entire artistic community one day.”

For now, during his tenure as a MacArthur Fellow, Rolland has other plans.

“More inventions. I have six more I’m working on that I believe will improve and enhance the bow and the experience of the musician who embraces it,” he said. “And I will try to relax, as well.”

Chelsea Conaboy of the Globe staff contributed. She can be reached at cconaboy@boston.com. Follow James Burnett on Twitter: @JamesBurnett

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